docs: def get(feature_name):
          """Returns the MetadataExtractor that can extract information about the
          provided feature name.
  
          Raises:
              UnsupportedFeature: If no extractor exists for the feature name.
  
          """
          implementations = MetadataExtractor._implementations()
          try:
              return implementations[feature_name]
          except KeyError:
              raise UnsupportedFeatureException(
                  'no MetadataExtractor registered for feature "{feature_name}" '
                  '(try any of the following: {supported_features})'
                  .format(feature_name=feature_name,
                          supported_features=', '.join(sorted(implementations))))